Question

Identify the homoleptic complexes with odd number of d-electrons in the central metal:

(A) [FeO₄]²⁻      (B) [Fe(CN)₆]³⁻

(C) [Fe(CN)₅NO]²⁻      (D) [CoCl₄]²⁻

(E) [Co(H₂O)₃F₃]

Choose the correct answer from the options given below :

• A. (B) and (D) only
• B. (C) and (E) only
• C. (A), (B) and (D) only
• D. (A), (C) and (E) only

Hint:

To identify complexes with odd numbers of d-electrons, determine the oxidation state of the central metal and subtract the oxidation state from the total number of electrons in the neutral atom.

Answer 1

The Correct Option is A

- (A) \([FeO_4]^{2-}\): Iron in this complex is in the +2 oxidation state, with \( d^6 \) electrons. Since 6 is an even number, this complex does not meet the requirement for an odd number of d-electrons.
- (B) \([Fe(CN)_6]^{3-}\): Iron in this complex is in the +3 oxidation state, with \( d^5 \) electrons. This gives an odd number of d-electrons, so this is a homoleptic complex with odd d-electrons.
- (C) \([Fe(CN)_6]^{2-}\): Iron is in the +2 oxidation state with \( d^6 \) electrons. This complex has an even number of d-electrons.
- (D) \([CoCl_4]^{2-}\): Cobalt in this complex is in the +2 oxidation state, with \( d^7 \) electrons. This gives an odd number of d-electrons, so this is a homoleptic complex with odd d-electrons.
- (E) \([Co(H_2O)_6]^{3+}\): Cobalt in the +3 oxidation state has \( d^6 \) electrons, which is an even number.

Thus, the correct answer is (1) (B) and (D) only.